conduit vs tray cable [RE-wrenches]

[Lawrence Elliott]

Thanks Jeffery for bringing up this issue of liquid tight conduit.

I recently attended a technical forum taught by Bill Brooks and although
quite good and informative I was somewhat disappointed that so much of
the module connection issues were on a roof and with little  use of
conduit.

I have been installing PV for over 15 years now.
For most of this time I have used conduit any time the module J box
design allowed it. With over 150 systems I have never installed a single
panel on a roof and that includes many urban settings.
My latest install involved the use of 48 100 watt Seimens SR100's. They
are all on DP&W racks on the ground.
In no way could I have put the panels on the roof due to orientation and
size.
Most installers in the Northwest that I know rarely mount panels on a
roof. Most customers don't want them there either.

When I first started using conduit  I simply glued male threaded ends to
the Carflex and used a standard nut with a silicone O ring to seal. I
also used THHN wire and always rated to no more than 2% voltage drop.
I discovered that the -2 wire recommended by Bill Brooks at the seminar
is exactly what I had always used even though I did not really know it
at the time. Seems that in all the supply houses I have bought from not
a single one even stocks just THHN. It is all -2.

In systems subjected to extreme desert heat on mountain repeater sites,
torrential short lived downpours and blistering heat on remote desert
water pumping systems using trackers, and simple mountain cabins I have
yet to see one failure of either the conduit or wire and I have never
seen even a hint of moisture in a J box.

I have seen trackers, ground mounted arrays and fixed pole mounted
arrays installed by others using tray cable and in every case they
looked very messy and cobbled together.
Multiple cables run to a combiner box on a tracker of say 18 modules
wired for 24 volts looks like a real mess.
The same unit in 1/2" conduit is primo and clean.

As to the 60 degree C ( 140 degree F) wet versus the 105 degree C (220
degree F) dry controversy I do wish it would be resolved with some
realistic testing.
I have been back to some of my sites that have been in extreme heat,cold
and wet for 13 years and see absolutely no signs of a degraded wire or
conduit.
In some cases I have seen USE or RHW used by others at the same site
looking pretty ratty.

And as to the use of glue and conduit ends with CarFlex.'

I had a supplier who found an obscure but valid reference in one of the
CarFlex tech sheets that actually allowed this and was listed by UL.
I also had it confirmed by a Portland  Oregon Code Inspector who
attended the referenced tech forum

I have yet to see one of these glued conduits fail but I have seen
expensive Thomas and Betts, Bridegport  and Hubble ends separated and in
some cases UV has made them very brittle with the non silicone O ring
turned to powder.



Larry Elliott

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